Since no one answered the OP's question, I have three of them $$ (18"X18")(my coach has only three jacks) and they have worked well. Coach like mine in next site sank into ground and had a hard time getting jack out from hole. He had to air up and retract jacks and then crawl under and using long pole and shovel help jack retract. Mine only bowed about 1/2". At next stop it had returned to original shape.
I've had many wooden ones and they either ended up breaking or squashing in the middle.
Good luck on whatever you decide.